Blood parameter measurement system
A blood parameter measurement system has a monitor configured to provide an oxygen saturation measurement based upon the absorption of two wavelengths of optical radiation by a tissue site. A software upgrade is installable in the monitor so as to enable the monitor to operate in conjunction with a multiple wavelength sensor. A wavelength controller is adapted to the upgrade so as to drive the sensor.
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The present application claims priority benefit under 35 U.S.C. §119(e) from U.S. Provisional Application No. 60/428,419, filed Nov. 22, 2002 entitled “Blood Parameter Measurement System,” which is incorporated herein by reference.
BACKGROUND OF THE INVENTIONPulse oximetry is a noninvasive, easy to use, inexpensive procedure for measuring the oxygen saturation level of arterial blood. Pulse oximeters perform a spectral analysis of the pulsatile component of arterial blood in order to determine the relative concentration of oxygenated hemoglobin, the major oxygen carrying constituent of blood. By providing early detection of decreases in the arterial oxygen supply, pulse oximetry reduces the risk of accidental death and injury. As a result, pulse oximeters have gained rapid acceptance in a wide variety of medical applications, including surgical wards, intensive care units, general wards and home care.
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The Beer-Lambert law provides a simple model that describes a tissue site response to pulse oximetry measurements. The Beer-Lambert law states that the concentration ci of an absorbent in solution can be determined by the intensity of light transmitted through the solution, knowing the pathlength dλ, the intensity of the incident light I0,λ, and the extinction coefficient εi,λ at a particular wavelength λ. In generalized form, the Beer-Lambert law is expressed as:
Iλ=I0,λe−d
where μa,λ is the bulk absorption coefficient and represents the probability of absorption per unit length. The minimum number of discrete wavelengths that are required to solve EQS. 1-2 are the number of significant absorbers that are present in the solution. For pulse oximetry, wavelengths are chosen such that, normally, there are only two significant absorbers. These are oxygenated hemoglobin (HbO2) and deoxygenated hemoglobin (Hb). Thus, pulse oximetry measurements are conventionally made at two wavelengths including a red wavelength, such as 660 nm, and an infrared wavelength, such as 940 nm.
There is a need to provide a noninvasive, easy to use, inexpensive procedure to measure multiple blood parameters, other than, or in addition to, HbO2 and Hb. For example, hemoglobin species that are also significant under certain circumstances are carboxyhemoglobin (HbCO) and methemoglobin (MetHb). Other blood parameters that may be measured to provide important clinical information are blood glucose and total hematocrit (Hct), to name a few. An advantageous solution is to provide a software upgrade for conventional pulse oximetry so as to achieve multiple-wavelength capability, that is, the ability to measure tissue site response to optical radiation of three or more wavelengths. Such a software upgrade can be readily applied to current pulse oximetry system designs and to the widespread installed base of pulse oximeters and multiparameter patient monitors to increase measurement capabilities to include a range of important blood parameters in addition to, or instead of, oxygen saturation.
One aspect of a blood parameter measurement system is a monitor configured to provide an oxygen saturation measurement based upon the absorption of two wavelengths of optical radiation by a tissue site. A software upgrade is installable in the monitor so as to enable the monitor to operate in conjunction with a multiple wavelength sensor. A wavelength controller is adapted to the upgrade so as to drive the sensor.
Another aspect of a blood parameter measurement system is a multiplicity of emitters configured to transmit at least three distinct wavelengths of optical radiation into a tissue site. At least one detector is configured to receive the radiation after attenuation by the tissue site and to generate a corresponding detector signal output. A wavelength controller has a drive signal input and a sensor control output and is adapted to sequentially enable the emitters.
A further aspect of a blood parameter measurement system is a method having the steps of communicating a drive signal from a monitor to a sensor and synchronizing the sensor with the monitor. Additional steps include sequentially enabling a plurality of emitters of the sensor and communicating a sensor signal from the sensor to the monitor.
An additional aspect of a blood parameter measurement system is a multiple wavelength sensor means for illuminating a tissue site with at least three wavelengths and detecting a corresponding tissue site response. The system includes a software upgrade means for enabling a pulse oximetry monitor to drive the sensor and process a corresponding sensor signal. The system also includes a wavelength controller means for interfacing between the software upgrade means and the multiple wavelength sensor means.
As shown in
As shown in
The sensors 610, 660 described with respect to
As shown in
In operation, the sync output 722 initializes the output multiplexer 740 so that a first pair of sensor control outputs 702 is selected, which selects a predetermined pair of emitters 620 (
In operation, the sync output 722 initializes the switch control 830 so that a first switch control output 805 is selected, which actuates a switch or switches that connect a predetermined pair of emitters 620 (
These elements may be incorporated into an adaptive sensor 610 (
As shown in
The LED enable sequence 1131, 1133, 1135 can be any number of patterns. For example, for a three-wavelength sensor, the LED enable pattern can be 1, 2, 3, 1, 2, 3, . . . as shown, where the numbers correspond to individual LEDs, such as an IR LED and two red LEDs. As another example, the LED enable pattern can be 1, 2, 1, 3, 1, 2, 1, 3, . . . Further, the duration or duty cycle of LED enable periods can vary. For example, for a three-wavelength sensor, the duration for each LED enable period and each dark period can be the same, such that each LED has a 16.7% duty cycle. As another example, the IR LED can have a 28.6% dutv cycle and the red LEDs can each have a 14.3% duty cycle, to name just a few timing variations.
A blood parameter measurement system has been disclosed in detail in connection with various embodiments. These embodiments are disclosed by way of examples only and are not to limit the scope of the claims that follow. One of ordinary skill in the art will appreciate many variations and modifications.
Claims
1. A blood parameter measurement system comprising:
- a monitor configured to provide an oxygen saturation measurement based upon the absorption of two wavelengths of optical radiation by a tissue site;
- a software upgrade installable in said monitor so as to enable said monitor to operate in conjunction with a multiple wavelength sensor; and
- a wavelength controller adapted to said upgrade so as to drive said sensor, wherein said upgrade comprises: sampling software providing a drive waveform for said sensor; and signal processing software adapted to demodulate a multiplexed signal from said sensor.
2. The blood parameter measurement system according to claim 1 wherein said drive waveform comprises:
- a header interval that controls said wavelength controller; and
- an emitter drive interval that enables drive current to said sensor.
3. The blood parameter measurement system according to claim 2 wherein said header interval comprises a sync period decodable by said wavelength controller so as to synchronize said wavelength controller and said upgrade.
4. The blood parameter measurement system according to claim 2 wherein said header interval comprises a command interval decodable by said wavelength controller so as to allow said upgrade to command said wavelength controller.
5. A blood parameter measurement system comprising:
- a monitor configured to provide an oxygen saturation measurement based upon the absorption of two wavelengths of optical radiation by a tissue site;
- a software upgrade installable in said monitor so as to enable said monitor to operate in conjunction with a multiple wavelength sensor; and
- a wavelength controller adapted to said upgrade so as to drive said sensor, wherein said wavelength controller is located in an adapter cable, and said adapter cable provides an interface between the sensor port of said monitor and said sensor.
6. A blood parameter measurement system comprising:
- a monitor configured to provide an oxygen saturation measurement based upon the absorption of two wavelengths of optical radiation by a tissue site;
- a software upgrade installable in said monitor so as to enable said monitor to operate in conjunction with a multiple wavelength sensor; and
- a wavelength controller adapted to said upgrade so as to drive said sensor, wherein said wavelength controller is integrated into said sensor.
7. The blood parameter measurement system according to claim 6 wherein said wavelength controller is co-located with multiple LEDs within an emitter component, said emitter component adapted to substitute for a two-wavelength emitter component within a pulse oximetry sensor.
8. A blood parameter measurement system comprising:
- a monitor configured to provide an oxygen saturation measurement based upon the absorption of two wavelengths of optical radiation by a tissue site;
- a software upgrade installable in said monitor so as to enable said monitor to operate in conjunction with a multiple wavelength sensor; and
- a wavelength controller adapted to said upgrade so as to drive said sensor, wherein said wavelength controller comprises: a sensor control configured to route a drive signal to a select one of a plurality of sensor emitters; and a sync detector adapted to decode a sync interval on said drive signal so as to synchronize the operations of said software upgrade and said wavelength controller.
9. The blood parameter measurement system according to claim 8 wherein said wavelength controller further comprises a command decoder adapted to decode a command interval on said drive signal so as to accept commands from said software upgrade.
10. The blood parameter measurement system according to claim 8 wherein said wavelength controller further comprises a transmitter configured to communicate sensor information to said monitor on conductors that communicate said drive signal.
11. The blood parameter measurement system according to claim 8 wherein said sensor control comprises an output multiplexer that routes said drive signal to selected emitters of said sensor.
12. The blood parameter measurement system according to claim 8 wherein said sensor control comprises:
- a plurality of switches configured to connect and disconnect said drive signal and emitters of said sensor; and
- a switch control configured to actuate select ones of said switches.
13. A blood parameter measurement method comprising the steps of:
- communicating a drive, signal from a monitor to a sensor;
- synchronizing said sensor with said monitor;
- sequentially enabling a plurality of emitters of said sensor; and
- communicating a sensor signal from said sensor to said monitor, wherein said synchronizing step comprises the substeps of: inputting said drive signal to a wavelength controller; and decoding a header interval of said drive signal so as to detect a sync event.
14. The blood parameter measurement method according to claim 13 wherein said enabling step comprises the substeps of:
- selecting a predetermined first emitter pair of said sensor in response to said sync event;
- routing said drive signal to said first emitter pair, and
- activating said first emitter pair during a drive interval of said drive signal.
15. The blood parameter measurement method according to claim 14 wherein said enabling step comprises the further substeps of:
- deactivating said first emitter pair;
- selecting a predetermined second emitter pair to follow said first emitter pair;
- routing said drive signal to said second emitter pair and activating said second emitter pair during a drive interval of said drive signal.
16. A blood parameter measurement system comprising:
- a multiple wavelength sensor means for illuminating a tissue site with at least three wavelengths and detecting a corresponding tissue sfte response;
- a software upgrade means for enabling a pulse oximetry monitor to drive said sensor and process a corresponding sensor signal; and
- a wavelength controller means for interfacing between said software upgrade means and said multiple wavelength sensor means.
17. The blood parameter measurement system according to claim 16 wherein said software upgrade means comprises:
- a sampling controller means for generating an encoded drive signal; and
- a signal processing means for demodulating said sensor signal.
18. The blood parameter measurement system according to claim 17 wherein said wavelength controller means comprises a sync decoder means for synchronizing with said software upgrade means in response to said encoded drive signal.
19. The blood parameter measurement system according to claim 16 wherein said wavelength controller means comprises a sensor control means for routing a drive signal from said monitor to a selected one of a plurality of sensor emitters.
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Type: Grant
Filed: Nov 21, 2003
Date of Patent: Apr 11, 2006
Patent Publication Number: 20040107065
Assignee: Masimo Laboratories, Inc. (Irvine, CA)
Inventor: Ammar Al-Ali (Tustin, CA)
Primary Examiner: Michael Nghiem
Assistant Examiner: Demetrius Pretlow
Attorney: Knobbe, Martens, Olson & Bear, LLP
Application Number: 10/719,928
International Classification: A61B 5/00 (20060101);